Add ResourceKey to ResourcesChangedEventArgs

[rabbitism]

Currently when subscribing to IResourceHost.ResourceChanged event, we cannot know exactly which resource has been changed. Is it possible to add resource Key to this event args, just like PropertyChangedEventArgs?

[maxkatz6]

Most of the time it will be raised without resource key at all. I.e. when dictionary is initially attached, or owner changed. Basically with any operation that isn't simple Add(key,value)/Remove(key). Either way it might be useful.

[rabbitism]

Yes, I think it's still a valid case to raise an arg without key, but currently, GetResourceObservable(object key) is not working at all, it reacts to all resource changes, instead of the particular key.